A foamed urethane or a fiber assembly has been used as a cushion of a furniture, a bedding, a vehicle or the like, or as a buffer member of a clothing, a footwear or the like [e.g., a brassiere cup or a substrate thereof, a shoulder pad, and a substrate for a shoe insole (a sockliner or a shoe insert)]. For some applications, the foamed urethane is excessively elastic and poorly permeable to air, and its texture (hand or handle) is insufficient. In an application to be worn, particularly, the foamed urethane causes an uncomfortable humid state. Therefore, the fiber assembly has been used in an application which highly requires an excellent or soft texture or air-permeability. The fiber assembly, however, has drawbacks (e.g., a falling off of fibers and an insufficient cushion property or shape (configuration) stability). To overcome these drawbacks, a buffer member or the like comprising various fiber assemblies has been developed. The fiber assembly comprises a fiber web comprising a thermal adhesive component mixed in the web, and the fibers constituting the web are immobilized or fixed to each other by heating the fiber web from a surface thereof.
For example, Japanese Patent Application Laid-Open Publication No. 5-161765 (Patent Document 1) discloses a cushion comprising a fiber assembly comprising a highly crimped fiber having a number of crimps of not less than 50/25 mm and a degree of crimp of not less than 40%; and a sheath-core structure thermal adhesive fiber. The cushion has a structure formed by bonding the crimped fibers partly to each other with the sheath-core structure thermal adhesive fiber; and has a thickness of not less than 5 mm and a basic weight of not less than 200 g/m2. This document describes that a resin having a melting point lower than that of a core component (e.g., a resin component such as a polyester copolymer, a polyamide, or a polyolefine) is used as a sheath component of the sheath-core structure thermal adhesive fiber. In Examples of the document, a sheath-core structure fiber comprising an isophthalic acid-modified poly(ethylene terephthalate) as a sheath component is used and subjected to a heat treatment at 155° C. for 3 minutes.
Moreover, Japanese Patent Application Laid-Open Publication No. 8-851 (Patent Document 2) discloses a fiber-based wadding material comprising a structure comprising a crimped fiber which comprises an inelastic thermoplastic resin and has a fineness of 1 to 10 denier and a three-dimensional crimp owing to its latent ability of developing the crimp; and a thermal adhesive conjugated (or composite) fiber which comprises an elastic thermoplastic resin as a thermal adhesive component and has a fineness of 1 to 6 denier. The structure is three-dimensionally formed by opening and blending the crimped fiber and the thermal adhesive conjugated fiber to entangle the crimped fibers with each other or the crimped fiber with the adhesive fiber due to the three-dimensional crimping; and melting the adhesive fibers to integrate the adhesive fibers with each other or the adhesive fiber with the crimped fiber at most of the contacting points of these fibers. Both surfaces of the structure are substantially flat or plane, and the structure has a thickness of 1 to 30 mm; and an apparent density of 0.01 to 0.10 g/cm3. The elastic thermoplastic resin component shows an endothermic peak ranging from a room temperature to the melting point in a melting curve measured by a differential scanning calorimeter. This document discloses that, in a heat treatment at a temperature 10 to 40° C. higher than the melting point of the thermal adhesive component, the temperature rise process allows the fiber which has not yet developed a crimp to develop a fine, three-dimensional crimp to entangle the fibers with each other due to the three-dimensional crimping; and the heat treatment allows most of the contacting points of the thermal adhesive conjugated fiber with the fibers to form a thermally bonded point or area comprising the thermoplastic elastic resin by melting the thermal adhesive component. Specifically, in Examples, a mixture of the fibers is heat-treated with a hot air having a temperature of 200° C. for 5 minutes.
However, since a large adiathermancy of the mixed web seems to hinder a uniform heat conduction to the inside of the web, the above cushion wadding material or the cushion has neither a uniform percentage of crimp of the crimped fiber nor a uniform bonded ratio of the sheath-core structure thermal adhesive fiber in the thickness direction. Thus, the cushion or cushion wadding material has a poor cushion property and shape stability, and the falling off of the fibers is not effectively prevented.
Japanese Patent Application Laid-Open Publication No. 2003-293255 (Patent Document 3) discloses a needle-punched nonwoven fabric comprising a staple fiber. The staple fiber comprises a potential crimping polyester fiber which comprises two kinds of poly(trimethylene terephthalate)s having a difference in intrinsic viscosity of 0.05 to 0.4 (dl/g) therebetween and conjugated in a side-by-side structure. However, since the fibers are not fixed to each other or to other fibers at the intersecting or contacting points with an adhesive component, the nonwoven fabric has a low configuration stability and the fiber greatly falls off.
Further, Japanese Patent Application Laid-Open Publication No. 2003-342864 (Patent Document 4) discloses a cushion structure which comprises a conjugated staple fiber comprising a fiber-forming polyester polymer and a thermoplastic elastomer forming at least part of a surface of the conjugated staple fiber. The cushion structure has a density of 0.005 to 0.15 g/cm3 and a thickness of not less than 5 mm. In the cushion structure, the conjugated staple fibers are thermally bonded to each other at the intersecting points thereof to distribute the thermally bonded points sporadically. Additionally, the cushion structure has an impact resilience of not less than 50%, a hardness at 25% compression of not more than 300 N, and a strain due to durability to compression of not more than 13%. This document also discloses that a dry-heat treatment is preferred and conducted at a temperature 10 to 80° C. higher than the melting point of the thermoplastic elastomer to thermally melt-bond the conjugated staple fibers to each others. However, the cushion structure still has a poor cushion property and shape stability, and the falling off of the fiber cannot effectively be prevented.
Moreover, as for a cushion used for a seat of a vehicle, a train, an aircraft, or the like, Japanese Patent Application Laid-Open Publication No. 2003-250666 (Patent Document 5) discloses a resin molded product having a spring structure comprising at least two sheets having the same or different spring property. The resin molded product comprises a solid-core and/or hollow continuous filament (s) comprising at least a thermoplastic resin; and/or a solid-core and/or hollow short filament(s) comprising at least a thermoplastic resin. The continuous filament and the short filament have a random loop or curl. The resin molded product has a three-dimensional structure having a predetermined bulkiness and voids and formed by contacting and entangling the loop or curl filaments adjacent to each other to aggregate the filaments. The document discloses that the filament used for the molded product is obtained by forming a filament having a fineness of 0.3 to 3.0 mm from a mixture of a polyolefinic resin and a vinyl acetate resin, a vinyl acetate-ethylene copolymer or a styrene-butadiene-styrene copolymer; forming a loop having a diameter of 1 to 10 mm; and bringing the fibers into contact and entangling the fibers with each other. However, this cushion has an insufficient cushion property due to a large loop diameter and has a difficulty in a meticulous control of cushion property due to a large fineness.
Further, International Publication WO 91/19032 (Patent Document 6) discloses a cushion structure which comprises an inelastic polyol-series crimped staple fiber assembly as a matrix and has a density of 0.005 to 0.10 g/cm3 and a thickness of not less than 5 mm. The staple fiber assembly comprises an elastic conjugated fiber dispersed and mixed therein. The elastic conjugated fiber comprises an inelastic polyester and a thermoplastic elastomer which has a melting point 40° C. lower or more than 40° C. lower than that of a polyester polymer constituting the staple fiber, and the thermoplastic elastomer forms at least part of a surface of the conjugated fiber, and these fibers are thermally melt-bonded to each other at an intersected state. This document discloses that the conjugated fiber is treated with a hot water having a temperature of 95° C. to develop a crimp; a web comprising the crimped fiber is subjected to a heat treatment with a metal mold at 200° C. for 10 minutes to melt-bond the fibers to each other. However, this cushion structure deforms at a low temperature, and the fibers are easily separated or loosed at the intersecting points thereof. Additionally, neither the distribution of crimp nor bond of the fibers in the thickness direction is uniform. Therefore, the cushion structure has a low cushion property and form or shape retention property.
Moreover, a brassiere cup is a buffer member to be disposed in a brassiere in order to keep or retain the form or shape of the brassiere or the form of the breast. The brassiere cup widely used includes a sewn cup or a molded cup. This brassiere cup requires a soft or excellent texture, air-permeability for avoiding humidity, or the like, in addition to softness or elasticity, and form or shape retention property.
A brassiere cup satisfying those requirements is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2004-124266 (Patent Document 7). The document suggests a substrate for a brassiere cup, comprising a fiber web and a thermosetting resin. The fiber web comprises a conjugated fiber at least in 30% by mass, and the conjugated fiber comprises a poly(ethylene terephthalate) or polycarbonate copolymer resin component and a poly(butylene terephthalate) copolymer resin component. The fibers are bonded with the thermosetting resin, and the mass of the thermosetting resin is 0.25 to 2 times as much as that of the fiber web. This document discloses a method comprising the steps of entangling the conjugated fibers with each other by a needle-punching; spraying, impregnating, or coating the resulting web with a thermosetting resin as a binder; and curing the binder. Alternatively, the document discloses a method comprising the steps of entangling the conjugated fibers having a spiral crimp with each other by a needle-punching; spraying, impregnating, or coating the resulting web with a thermosetting resin as a binder; and curing the binder.
However, in the substrate sprayed or coated with the binder, the bonded area of the fibers tends to concentrate on the substrate surface, thereby the shape retention property of the substrate is not sufficient. On the other hand, for the substrate impregnated with the binder, the fiber has an excessively large bonded area, leading to a decrease in cushion property. Additionally, in this substrate, the potential crimping fiber is heated to develop a crimp by a common manner used in the step of curing the binder. Therefore, the degrees of the crimps in the surface and inside of the substrate are not uniform, resulting in lowering the cushion property. The use of the crimped fiber provides a less fiber entanglement due to the crimped fiber, and the fibers and crimped fibers are intertwined or entangled with each other by a needle-punching. In this case, recoverability or shape retention property is decreased.
Further, Japanese Patent Application Laid-Open Publication No. 2004-300593 (Patent Document 8) suggests a substrate for a brassiere cup, comprising a fiber web. The fiber web comprises a thermal adhesive fiber comprising at least a polyester obtained by copolymerization of a caprolactone as a constituent component; a potential crimping fiber having a melting point higher than the adhesion temperature of the thermal adhesive fiber; and other fiber(s) having a melting point higher than the adhesion temperature of the thermal adhesive fiber. In the fiber web, and the adhesive fiber, the crimping fiber, and other fiber(s) are contained in a ratio of 10 to 50% by mass, 20 to 90% by mass, and 0 to 70% by mass, respectively, and the fibers are intertwined with each other by a needle-punching. For this substrate, the thermal adhesive fiber is melted to lose its fiber form, and the potential crimping fiber is heated at 170° C. (that is, dry heated) to develop a crimp.
However, since the crimp of the fiber is ununiform in the inside the substrate, the substrate has an insufficient cushion property. Moreover, since in the inside of the substrate, neither the melt-bonding of the thermal adhesive fiber due to the dry-heating nor the entanglement of the fibers by the needle-punching is uniform, the shape retention property and cushion property of the substrate are decreased.
A shoe insole usually has a laminated structure comprising a single- or multi-layer sheet (or sheet-like matter). For example, Japanese Patent Application Laid-Open Publication No. 2004-41384 (Patent Document 9) discloses a shoe insole obtained by laminating a surface fabric or cloth, a lining fabric or cloth, and a single- or multi-layer intermediate sheet therebetween; and fusing the resulting laminate in a shape of a shoe insole by conducting a high-frequency current through the laminate and simultaneously bonding a peripheral area of the laminate. As mentioned above, a known shoe insole includes a shoe insole in which a filler comprising a single- or multi-layer fabric is disposed by between outer surface materials (such as a fabric or cloth) and a peripheral area of the filler to those of outer surface materials. Since such a shoe insole usually comprises a fiber, the shoe insole has an air-permeability and tends to prevent or suppress a foot bottom from becoming humid. Additionally, in order to increase the cushion property, a thermally contractive fiber is sometimes used for the filler.
However, since the filler is fixed only at its peripheral area, the strength of the shoe insole is insufficient. Moreover, it is difficult to form a shoe insole to fit to a shape or configuration of a foot bottom. Further, in order to improve the strength, the filler may be bonded with an adhesive to the outer surface materials. However, in this case, the air-permeability of the shoe insole is decreased.
In order to obtain air-permeability, cushion properties, fitness, Japanese Patent Application Laid-Open Publication No. 2002-223807 (Patent Document 10) suggests a fiber structure for a shoe insole, comprising a supporting layer; a fiber layer comprising a fiber upstanding or extruding from a surface of the supporting layer. The fiber structure comprises an adhesive crimped fiber having a percentage of crimp of not less than 5% in a ratio of not less than 20% by mass. The fiber layer comprises a melt-bonded layer formed by a thermally bonding of the adhesive crimped fibers; and a bulky layer which is highly bulky and disposed on the melt-bonded layer so as to form a surface of the fiber structure. This document discloses that a fiber structure comprising the adhesive crimped fiber comprising an ethylene-vinyl alcohol-series copolymer is sprayed with water from a surface adjacent to the supporting layer; and the resulting fiber structure is subjected to a heat treatment to immobilize a bottom area of the bulky fiber with the melt-bonded layer comprising the melt-bonding fiber and allow the bulky fiber to be upstanding, thereby forming the bulky layer.
However, this fiber structure requires to make the bulky layer thin in order to maintain the fiber-upstanding structure, and the fiber upstanding from the melt-bonded layer easily falls off. Therefore, the cushion property or (mechanical) strength tends to decrease.
In order to improve fitness to a foot bottom and air-permeability, a manner to contrive a structure of a shoe insole, for example, a structure or mechanism for introducing air to an inside of a shoe by attaching an air pump to a bottom of the shoe is suggested. Japanese Patent Application Laid-Open Publication No. 2000-166606 (Patent Document 11) suggests a ventilating member for a shoe sole. The ventilating member comprises a sheet comprising a polymeric elastic body or substance and a housing frame disposed on a surface of the sheet and having a peripheral area having a uniform height. In the ventilating member, the sheet surface in or within the housing frame is provided with a plurality of through-holes; a mesh sheet and water-proof air-permeable sheet are successively intruded or inserted in the housing frame; and the peripheral area of the housing frame is sealed.
However, since the insole having such a mechanism or structure is complicated, the insole requires an intricate production step(s) and readily breaks. Additionally, due to the low air-permeability of the insole, even an introduction of air to the insole tends to fail to prevent humidity at a sole of a foot (or a foot bottom).
Moreover, Japanese Patent Application Laid-Open Publication No. 63-235558 (Patent Document 12) discloses a thermally bonded nonwoven fabric under moisture obtained by spraying water on or to a web containing a conjugated fiber comprising an ethylene-vinyl alcohol copolymer and other thermoplastic resins; and heating the resulting web with a heating roller.
However, this nonwoven fabric has an ununiform distribution of bond of the fibers in the thickness direction of the nonwoven fabric and a low cushion property.    [Patent Document 1] JP-5-161765 (Claim 1, Paragraph No. [0011], and Examples)    [Patent Document 2] JP-8-851 (Claims 1 and 6 and Examples)    [Patent Document 3] JP-2003-293255 (Claim 1)    [Patent Document 4] JP-2003-342864 (Claim 1, Paragraph Nos. [0033] and [0034], and Examples)    [Patent Document 5] JP-2003-250666 (Claim 1, Paragraph Nos. [0001], [0012] to [0015], and [0046] to [0048])    [Patent Document 6] WO91/19032 (Claim 1, Page 6, upper right column, lines 24 to 26, and Examples)    [Patent Document 7] JP-2004-124266 (Claims 1 to 4, Paragraph No. [0027], and Examples)    [Patent Document 8] JP-2004-300593 (Claim 1, Paragraph No. [0044], and Examples)    [Patent Document 9] JP-2004-41384 (Claim 1)    [Patent Document 10] JP-2002-223807 (Claims)    [Patent Document 11] JP-2000-166606 (Claim 1)    [Patent Document 12] JP-63-235558 (Claim 1 and Examples)